The present invention relates to novel monomers used for preparing a photoresist copolymer, and a process for preparing the same. More specifically, it relates to monomers useful for forming photoresist polymer resins which have suitable properties for lithography processes using a light source employing deep ultraviolet region radiation, and a process for preparing the same.
In general, excellent etching resistance, heat resistance, adhesiveness and resolution are requisites for a photoresist resin. However, most of the conventional ArF photoresists have insufficient etching resistance, and cannot fully satisfy those properties. For example, the photoresist polymer resins comprising an alicyclic compound as a monomer have excellent etching resistance and resolution, but the absorbance of the photoresist at the wavelength of ArF light is so high that a pattern of high integrity and high resolution could not be obtained.
The object of the present invention is to solve the problems described above, and to provide novel photoresist monomers which impart excellent etching resistance and adhesiveness to photoresist polymers so as to be suitable for lithography processes using a deep ultraviolet light source.
Through intensive studies and research, the present inventors have developed monomers that can overcome the problems associated with developing a high-performance photoresist. As a result, they have found that when a compound having one or more hydroxyl groups or alkoxy groups, such as a compound of Chemical Formula 1 below, is used as a monomer for preparing a photoresist copolymer, adhesiveness of the photoresist to a silicon wafer is considerably enhanced, and a resist having excellent resolution and etching resistance can be developed.
The present invention provides a novel photoresist monomer represented by following Chemical Formula 1:
 less than Chemical Formula 1 greater than  
wherein, X represents CH2, CH2CH2, or oxygen;
R1 represents hydrogen, C1-C5 alkyl, or Rxe2x80x2OH;
R2 represents hydrogen; xe2x80x94OH, C1-C5 alkoxy, or xe2x80x94ORxe2x80x2xe2x80x94OH;
Rxe2x80x2 represents: 
xe2x80x83and
m is an integer from 1-5, n is 1 or 2 and p is 0 or 1.
Preferably Rxe2x80x2OH is selected from the group consisting of the following groups (2)-(9): 
The compounds of Chemical Formula 1 are synthesized by reacting (i) a compound represented by Chemical Formula 2 below with (ii) an alkyl compound having one or more hydroxyl group(s), in the presence of a base or acid catalyst in an organic solvent. 
wherein, X represents CH2, CH2CH2, or oxygen.
Examples of suitable alkyl compounds having hydroxyl substituent(s) include methanol, ethanol, propanol, ethylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,3-cyclopentanedimethanol, 1,2-cyclopentanedimethanol, 1,3-cyclopentanediol, and 1,2-cyclopentanediol.
As the acid catalyst, sulfuric acid, hydrochloric acid, nitric acid or acetic acid may be used. As the base catalyst, sodium hydride (NaH), potassium hydride (KH), calcium hydride (CaH2) or lithium diisopropyl amide (LDA) may be used. As the reaction solvent, tetrahydrofuran (THF), dimethylformamide, dimethylsulfoxide, dioxane, benzene, toluene, or xylene may be used.
The compounds according to the present invention can be effectively used as a monomer for synthesizing a photoresist resin for electron-beam, ArF, KrF, EUV, VUV (Vacuum Ultra Violet) and X-ray radiation, which can be employed in micro lithography processes to form high-integrity patterns of 0.15 xcexcm or less (DRAM of 1G or more). Since the monomers according to the present invention comprise one or more hydroxyl group or alkoxy group, adhesiveness can be considerably enhanced when they are employed in the synthesis of a photoresist resin, and a resist having excellent resolution and etching resistance can be developed therefrom.
Photoresist copolymer resins may be prepared by polymerizing a monomer of Chemical Formula 1 with at least one other monomer, for example with one or more alicyclic olefin monomers. Polymerization may be carried out using conventional bulk polymerization or solution polymerization processes.